Various electronic equipments are mounted on an automobile or the like serving as a mobile body. Therefore, wire harnesses are installed on the automobile or the like so as to transmit to these electronic equipments electric power from a power source (such as a battery) and control signals, etc., from a computer, etc. The wire harness includes a plurality of wires, and terminals fixedly secured respectively to end portions of these wires.
The wire is a so-called sheathed wire including a core wire composed of a plurality of conductive element wires twisted together into a round cross-section, and an insulative sheath covering the core wire. The terminal is formed of a conductive metal sheet or the like, and includes a wire connection portion to which the wire is electrically and mechanically connected, and an electrical contact portion adapted to be electrically and mechanically connected to the above electronic equipment.
In order to achieve a lightweight design of the above wire harness, there has been proposed a terminal-equipped wire (see, PTL 1) in which element wires of a core wire are made of aluminum or aluminum alloy. In the terminal-equipped wire disclosed in PTL 1, a sheath is removed from an end portion of the wire to thereby expose the core wire at this end portion, and an exposed portion of the core wire is superposed on a flat plate portion of a wire connection portion of a terminal. Ultrasonic vibration is applied to the exposed core wire portion and the flat plate portion by a known ultrasonic welding machine, so that the core wire and the flat plate portion are welded together. Accordingly the terminal is fixedly secured to the end portion of the wire in electrically-connected relation thereto.
In the terminal equipped-wire disclosed in the above-mentioned PTL 1, however, the core wire is formed by twisting the plurality of element wires together, and therefore those of the plurality of element wires disposed at a central portion of the core wire are not held in contact with the terminal. Therefore, the electrical resistance of those of the plurality of element wires held out of contact with the terminal tended to increase. Furthermore, the element wires are made of aluminum or aluminum alloy, and generally an oxide film is liable to develop on their surfaces, and also the element wires are equal to each other in the degree of deformation. Therefore friction was less liable to develop between the element wires, so that it was difficult to remove the oxide film between the element wires, and therefore it was difficult to keep the electrical resistance between the plurality of element wires to a low level.